The second edition of the
Ordo cantus Missae (1988), which gives the various Gregorian chants to use for every day and celebration. This book is designed to be used alongside a copy of the 1908
Graduale Romanum. For more information about the layout of the OCM, see
http://www.ccwatershed.org/blog/2013/jul/29/how-does-one-use-ordo-cantus-missae/.
Note that this edition of the OCM is keyed into the Missale Romanum, editio typica altera (1975).